Known apparatus for this purpose comprises a sleeve portion which is capable of being brought into engagement with the closure cap, drive means for driving a head portion which is capable of being connected to the sleeve portion by a slipping clutch to limit the torque which can be transmitted, and means for lowering the head portion and the sleeve portion on to the screw cap for carrying out the screwing operation.
Apparatuses of this kind are used primarily in the drinks industry, where there is a requirement for the bottles of drink to be closed by the bottler in as short a period of time, and in the most rational manner, possible. It is particularly important, in the bottle closure operation, for the closure cap to be screwed on to the bottle with only a limited torque, as otherwise the consumer cannot open the bottle by hand. In addition, if the torque applied is excessively high, there is a danger that the closure cap may be damaged when it is screwed on, with the result that the closure is not sealed.
The invention also relates to a process for screwing a screw cap on to the mouth of a bottle by apparatus having a sleeve portion which is capable of being brought into engagement with the closure cap, and a drive means. In this process, the completely filled bottles are moved, on an intermittently operated conveyor line, to a position aligned with the axis of the screwing-on apparatus, with the closure caps already loosely laid on the mouths of the bottles. The screwing-on head of the screwing-on apparatus is lowered on to the bottle and raised, after the screwing-on process has been completed, to permit the positioning of a fresh bottle to be closed with a screw cap.
Many different forms of screwing-on apparatus are already known in which the actual screwing-on head is force-lockingly connected to the drive means by a slippling clutch. Thus, for example German "Gebrauchsmuster" No. 71 48 902.6 discloses a screwing-on head wherein the lower part of the head, which is engaged with the screw cap, stops moving when a predetermined maximum torque is reached. In this arrangement, the slipping clutch comprises balls which are pressed by spring loading into corresponding recesses on the co-operating portion of the clutch. When the maximum torque is reached, the balls come out of the recesses so that the co-operating portion of the clutch comes to a halt.
A serious disadvantage of apparatus of this kind in that, when the head is lowered, the closure cap comes into contact therewith, whilst the entire apparatus is rotating at full speed. This is a serious disadvantage, in particular, with those closure caps which have an internal seal projecting into the mouth of the container. Such internal seals are in part-turned over rearwardly during the operation of fitting the cap in place, in order to provide a particularly good sealing action. This requires the screw cap to be pressed on to the mouth of the bottle in a particularly accurate manner, and also requires that the actual process of screwing the cap on to the bottle should be begun in a careful manner. This is not possible with the known apparatus, as the closure caps are easily tilted when the screwing-on process is immediately begun at full rotary speed of the apparatus, so that there is no longer any guarantee that the optimum sealing action will be achieved. In addition, because the fitting head is applied to the closure cap while rotating at full speed, wear phenomena can appear on the top of the cap, which have a disadvantageous effect, particularly when the surfaces of the cap bear printing.
A further disadvantage of most of the known forms of apparatus is that the lower part of the fitting head is of relatively large mass. As a result, the mass inertia which is produced by the rotary movement of the fitting head can cause undesired torque to be applied to the closure cap, even after the slipping clutch has become disengaged, and such undesired torque results in the above-described disadvantages.
The problem of the present invention is therefore that of avoiding the disadvantages of the known art and, in particular, of providing apparatus for screwing a screw cap on to the mouth of a bottle, which provides for a precise and careful start to the screwing-on process and wherein no undesired additional torques are applied to the cap after the screwing-on process has been completed.